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Chemistry
WAEC / WASSCE 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
14.8 g of a salt (z)dissolved in 250 cm3 of distilled water gives a concentration of 0.80 mol dm-3. Calculate the molar mass of the salt (z).
A
13.5 g mol-1
B
18.5 g mol-1
C
47.4 g mol-1
D
74.0 g mol-1
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
250cm3 of distilled water contains 14.8g of salt(z)
1cm3 of distilled water will contain \(\frac{14.8 x 1}{250}\) of salt (z)
:. 1000cm3 of distilled water will contain \(\frac{14.8 x 1 x 1000}{250}\) = 59.2g/dm33 = \(\frac{concentration in g/dm3}{molar mass}
0.80 = \(\frac{59.2}{molar mass}\)
molar mass = \(\frac{59.2}{0.80}\) = 74.0 g/mol
Source: Myschool Past Questions Archive (Record #37152)
Chemistry
WAEC / WASSCE 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
How many atoms are there in one mole of hydrogen gas? [Avogadro's constant = 6.02 x 1023mol-1]
A
1.2 x 10 23
B
6.0 x 10 23
C
1.2 x10 24
D
6.0 x 10 24
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
One mole of hydrogen gas has 6.02 x 1023 molecules, and one molecule of hydrogen gas contains 2 atoms of hydrogen
therefore, one mole of hydrogen gas will contain 2 x 6.02 x10^23 atoms
= 1.2 x 10^24 hydrogen atoms
Source: Myschool Past Questions Archive (Record #37159)
Chemistry
WAEC / WASSCE 2007
Stoichiometry, Mole Concept & Volumetric Analysis
What is the IUPAC name of the compound represented by the molecular formula NaCIO4?
A
Sodium tetraoxochlorate (l)
B
Sodium tetraoxochlorate (IV)
C
Sodium tetraoxochlorate (VI)
D
Sodium tetraoxochlorate(VII)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #37179)
Chemistry
WAEC / WASSCE 2007
Periodic Table & Periodicity
When air is successively passed through sodium hydroxide solution, alkaline pyrogallol and then concentrated tetraoxosulphate (VI) acid, its remaining components are
A
oxygen and water vapour
B
oxygen and nitrogen
C
carbon (IV) acid and noble gases
D
nitrogen and noble gases
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #37183)
Chemistry
WAEC / WASSCE 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following gases is light than air?
A
CO2
B
SO2
C
HCI
D
NH3
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #37186)
Chemistry
WAEC / WASSCE 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following statements is true of the molecules of a gas under ideal conditions? The molecules
A
move at random
B
undergo inelastic collisions
C
attract each other
D
occupy a large volume
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #37188)
Chemistry
WAEC / WASSCE 2007
Chemical Energetics & Thermochemistry
Solution
In which of the following compound (s) will heat be absorbed on adding water?
l. KNO\(_3\) II. Concentrated H\(_2\)SO\(_4\) III. NH\(_4\)CI
A
I only
B
lll only
C
l and lll only
D
ll and lll only
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
KNO\(_3\) and NH\(_4\)Cl both undergo endothermic.
Source: Myschool Past Questions Archive (Record #37189)
Chemistry
WAEC / WASSCE 2007
Oxidation, Reduction & Redox Reactions
Consider the reaction represented by the equation: Ca(OH)2(aq) + CO 2(g) → CaCO3(s) + H 2O(l)
in the reaction above, CO 2 acts as
A
an acidic oxide
B
an oxidizing agent
C
a basic oxide
D
a dehydrating agent
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #37193)
Chemistry
WAEC / WASSCE 2007
Acids, Bases, pH & Salts
Which of the following compounds is a basic salt?
A
Mg(NO3)2
B
(NH4)2SO4
C
K4Fe(CN)6
D
Zn(OH)CI
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #37194)
Chemistry
WAEC / WASSCE 2007
Reaction Rates & Chemical Equilibrium
Solution
What process is illustrated below? S(s) ⇌H2O⇌ S (aq)
A
Decomposition of a solid
B
Melting of a solid
C
Formation of saturated solution of a solid
D
Sublimation of a solid
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
From the given equation:
\(S_{(s)} ⇌ S_{(aq)}\) (in the presence of (\(H_2O\))
The solid form has changed to an aqueous solution upon dissolution in water. Due to the presence of the reversible reaction arrow ⇌, the solution (aqueous) formed is saturated, this is because a saturated solution is an equilibrium system
Source: Myschool Past Questions Archive (Record #37201)
Chemistry
WAEC / WASSCE 2007
Stoichiometry, Mole Concept & Volumetric Analysis
A solution of a salt X reacts with AgNO3 solution to give white precipitate which dissolves in excess aqueous ammonia. X contains
A
CI-
B
Pb 2+
C
SO 2-
D
Zn2+
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #37202)
Chemistry
WAEC / WASSCE 2007
Reaction Rates & Chemical Equilibrium
Consider the reaction represented by the following equation: N2(g) + 3H2(g) ⇌ 2NH3(g); ∆H = - 92kJmol1. Finely divided iron is used as catalyst in the reaction in order to
A
lower the value of ∆H
B
increase the time for attainment of equilibrium
C
shorten the time for attainment of equilibrium
D
decrease the yield of ammonia
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #37203)
Chemistry
WAEC / WASSCE 2007
Electrolysis & Electrochemical Cells
Which of these cell notations is the correct representation of a Daniell cell?
A
Zn(s) / Zn2+(aq) // Cu2+(aq)/Cu(s)
B
Cu(s) / CU2+(aq) // Zn2+(aq) / Zn(s)
C
Zn2+(aq) / Zn(s) // Cu2+(aq) /Cu(s)
D
Cu2+(aq) / Cu(s) // Zn(s) / Zn2+(aq)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #37206)
Chemistry
WAEC / WASSCE 2007
Oxidation, Reduction & Redox Reactions
Solution
What is the oxidation number of chromium in K2CrO4?
A
+1
B
+2
C
+4
D
+6
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
K2CrO4 (O.N of K) X 2 + O.N of Cr + (O.N of oxygen) X 4 = 0
1 X 2 + X + -2 X 4 = 0
2 + x + -8 = 0
2 + x - 8 = 0
x = 8 - 2 = + 6
Source: Myschool Past Questions Archive (Record #37230)
Chemistry
WAEC / WASSCE 2007
Electrolysis & Electrochemical Cells
What product is formed at the cathode during the electrolysis of concentrated sodium chloride solution using carbon electrodes?
A
Chlorine
B
Hydrogen
C
Oxygen
D
Sodium
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #37231)